1. Technical Field
The present invention relates to a controller for processing a corner part in a process path.
2. Description of Related Art
Generally, in a laser cutting process, the cutting direction is changed to generate a corner part (edge part). As the angle of the corner part becomes acuter, heat applied from a laser becomes excessive. A process failure may occur due to melted matter (dross) or self-burning, and as a result an uncuttable state occurs.
To suppress heat applied to a corner part (edge part), there is a case that a laser output is temporarily stopped in a corner part to provide cooling time and laser pulses are output (edge process) at the time of restarting the cutting after the cooling time. Alternatively, an operation (switch-back operation) is performed, of cutting a corner part from the vertex only by predetermined distance, temporarily stopping a laser output to have time of cooling the cut part, after the cooling, moving the laser output backward in the cut process path to the vertex of the corner part, and restarting the cutting along the process path. Whether such a process is performed or not is determined according to the angle formed in the corner part. Usually, a controller used in the laser cutting process analyzes a process path and makes the decision.
Japanese Patent No. 3,211,902 discloses a processing method of edge processing in accordance with the angle of a corner part generated by two cutting paths. Japanese Patent No. 3,825,123 discloses a process method and a controller, in the case of cutting the outside of an acute corner part, edge processing by analyzing the angle of the corner part of paths instructed by a process program, not actual process paths.
FIG. 12 is a diagram showing a corner part constructed by two linear main process paths in a related art. As shown in FIG. 12, an angle θ1 is generated between two linear main process paths ab and bc. In the case of cutting so as to obtain a relatively acute-angled corner part, by analyzing the two process paths ab and bc, the angle θ1 can be obtained.
FIG. 13 is a diagram showing a corner part constructed by two linear main process paths and a circular-arc path in a related art. In FIG. 13, a small circular-arc path ef is inserted between two linear paths de and fg. Due to the circular-arc path ef, a smooth, rounded corner part is formed.
However, in the case shown in FIG. 13, a controller recognizes an angle θ2 generated between the cut path de in front of the rounded-corner part and a tangent line eh at the point “e” on the circular-arc path ef. As understood from FIG. 13, the angle θ2 is an obtuse angle. In other words, the controller determines a part having a relatively acute angle in a shape to be cut as an obtuse-angle part. In such a case, the edge process cannot be performed properly.
Further, Japanese Patent Nos. 3,211,902 and 3,825,123 are limited to the case where a corner part to be cut has an acute angle formed by two linear main process paths. Consequently, the techniques disclosed in Japanese Patent Nos. 3,211,902 and 3,825,123 cannot be applied to a corner part obtained by inserting a small circular-arc path or a small linear path between two linear main process paths.
The present invention has been achieved in view of such circumstances and an object of the invention is to provide a controller capable of properly processing a corner part even in the case where a small circular-arc path or a small linear path is inserted between two main process paths.